The invention relates to fluid flow sensors and to arrangements for measuring the condition of pressure and/or velocity of the flow of a fluid in a passage and to accomplishing a control function on the basis of those conditions. More particularly, the invention is related to such apparatus having the capability to average the measured pressure and velocity of fluid flow across the width of a fluid flow duct such that air flow distribution within the duct is not critical to the functioning of a sensor.
Fluid flow measuring arrangements are illustrated in the following patents:
U.S. Pat. No. 1,087,929; Dodge; 2-24-14 PA0 U.S. Pat. No. 3,751,982; Lambert; 8-14-73 PA0 U.S. Pat. No. 1,311,798; Bristol; 7-29-19 PA0 U.S. Pat. No. 2,441,042; Stoll; 5-4-48 PA0 U.S. Pat. No. 3,273,390; Brown; 9-20-66 PA0 U.S. Pat. No. 3,667,494; Haase; 6-6-72 PA0 U.S. Pat. No. 2,911,787; Barry; 11-10-59 PA0 U.S. Pat. No. 3,889,536; Sylvester; 6-17-75
Attention is particularly directed to the Sylvester patent, U.S. Pat. No. 3,889,536 issued June 17, 1975 and assigned to the assignee of the present invention. A flow measuring and monitoring apparatus is shown therein having a Venturi tube positioned in a duct, the Venturi tube containing a first pressure sensing tap and a second pressure sensing tap being located in the duct but remote from the first pressure sensing tap. A means for comparing the pressures at the two taps yields a measurement of the pressure and/or velocity of fluid flowing through the duct. To amplify the pressure differential sensed by the two taps, an obstruction is provided in the passage adjacent the Venturi tube. It is further desirable, however, that the pressure and velocity of fluid flowing through the duct be measured across the entire duct rather than at localized points in the duct to permit more accurate and consistent control of fluid regulating apparatus.